Moving to an area with higher levels of air pollution is linked to weight gain in young children, according to a major natural experiment conducted in Catalonia. The study, which was conducted by the IDIAP Jordi Gol in collaboration with the Barcelona Institute for Global Health (ISGlobal), an institution supported by the “la Caixa Foundation,” offers additional proof in favor of initiatives to lessen air pollution.
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The interaction of genes, lifestyle choices, physiological factors, and social factors causes childhood obesity and overweight. Exposures to the environment, like air pollution, could also be important. However, it is still unclear whether there is a link and whether it is causal between air pollution and childhood obesity (i.e., whether air pollution directly causes obesity or overweight).
A good way to investigate whether the two are linked is to see what happens when a child is suddenly exposed to higher or lower levels of air pollution as a result of moving to a different home address. This is what we call a natural experiment.
Martine Vrijheid, Head, Childhood and Environment Research Group, Barcelona Institute for Global Health
A group led by Vrijheid used this natural experiment study design in this research, which was funded by the Social Observatory of “la Caixa” Foundation, to determine whether variations in air pollution exposure due to residential relocation were connected to changes in body mass index (BMI). The research included 46,644 children and adolescents (aged 2 to 17) who relocated once between 2011 and 2018 and were enrolled in primary healthcare in Catalonia.
Before and after each participant moved, the research group estimated the annual levels of NO2, PM10, and PM2.5 particulate matter in their previous residences. BMI was calculated using weight and height at the primary care facilities both before and 180 days or more after the relocation.
Weight Gain After Moving to More Air Pollution
According to the analysis, relocating to an area with higher air pollution levels was linked to a slight rise in BMI. All pollutants had this effect, and it was more pronounced in preschoolers and elementary school students. Moving to a less polluted area, however, had no discernible impact on BMI.
This may be because reductions in air pollution levels seem to be less relevant for those who were already exposed to high levels of pollution.
Sarah Warkentin, Study First Author and Researcher, Barcelona Institute for Global Health
Surprisingly, moving to areas with comparable levels of air pollution was associated with lower BMI. “This could be because these areas are more walkable or have more play areas for children,” notes Warkentin. It could also be due to the stress of moving. In contrast to some studies in the United States, the effect of air pollution on weight was unaffected by socioeconomic status.
The biological mechanisms that connect air pollution to weight gain are not completely understood, but they may include oxidative stress, adipose tissue inflammation, decreased glucose uptake, hormonal disruption, changes in metabolism, or decreased lung function.
More traffic may also cause behavioral changes, such as less time spent outdoors, which may result in weight gain. The researchers were unable to include these behavioral changes in their analysis because the study relied on available data from primary health care centers in Catalonia.
“However, the data collected routinely by primary healthcare professionals allowed us to perform a very large natural experiment in a very large number of children and adolescents. This type of study could be replicated in the future to study the impact of the environment on other health problems,” adds Talita Duarte-Salles, Head of the “Real World Epidemiology” research group at IDIAP Jordi Gol.
Our findings suggest that moving to areas with higher levels of air pollution can lead to weight gain in young children. They also provide further evidence for reducing air pollution levels, in addition to other community interventions, to prevent childhood obesity and overweight.
Martine Vrijheid, Head, Childhood and Environment Research Group, Barcelona Institute for Global Health
The authors emphasize that, while the magnitude of the observed associations is small, the effect on global public health could be significant, given that 56% of the world’s population lives in urban, polluted areas.
Journal Reference:
Warkentin, S., et al. (2023). Changes in air pollution exposure after residential relocation and body mass index in children and adolescents: A natural experiment study. Environmental Pollution. doi.org/10.1016/j.envpol.2023.122217.
Source: https://www.isglobal.org/